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Writing Groovy Classes with src/

The src/ directory is used for structured, reusable Groovy code inside Jenkins Shared Libraries. This is where complex logic belongs, not in Jenkinsfiles or vars/.

Purpose of src/​

Use src/ for:

  • Complex business logic
  • Utilities and helpers
  • Validation logic
  • Reusable services

Avoid:

  • Defining pipeline stages directly
  • Long shell scripts

Mandatory Package Structure​

All classes in src/ must use a package name.

Example structure:

src/
└── com/company/ci/
    └── PipelineUtils.groovy

Package declaration:

package com.company.ci

Without a package, Jenkins will fail to load the class.

Example Utility Class​

package com.company.ci

class PipelineUtils {

  def validateEnv(String env) {
    if (!['dev','qa','prod'].contains(env)) {
      throw new IllegalArgumentException("Invalid env: ${env}")
    }
  }

  def notifyTeam(String msg) {
    println "NOTIFY: ${msg}"
  }
}

Using src Classes from vars​

def call(Map cfg = [:]) {
  def utils = new com.company.ci.PipelineUtils()
  utils.validateEnv(cfg.env)
  echo "Environment validated"
}

This keeps:

  • vars → orchestration
  • src → logic

Accessing Pipeline Steps​

Important rule:

  • src classes do not automatically have access to pipeline steps

Correct pattern:

class PipelineUtils {
  def steps

  PipelineUtils(steps) {
    this.steps = steps
  }

  def runCmd(String cmd) {
    steps.sh cmd
  }
}

Usage:

def utils = new com.company.ci.PipelineUtils(this)
utils.runCmd('ls -la')

Error Handling in src​

  • Throw exceptions for invalid states
  • Let Jenkins handle failures
  • Avoid swallowing errors
throw new RuntimeException("Validation failed")

Common Mistakes​

  • No package declaration
  • Putting pipeline stages in src
  • Trying to call sh directly without steps
  • Overengineering small logic

Best Practices​

  • Keep src classes pure and testable
  • Pass steps explicitly when needed
  • Keep Jenkinsfile and vars thin
  • Use meaningful package names

Interview Focus Areas​

  • Why src needs package names
  • Difference between vars and src
  • How pipeline steps are accessed safely